LONGITUDE OF MOKATTAM. 



269 



(by -which Mokattam time was determined). It will be thus seen that signals 

 given by a sidereal clock or chronometer would be observed by a solar 

 chronometer, and vice versa, so that (on account of the acceleration of sidereal 

 on solar time) the observer receiving signals would, in all cases, register every 

 variety of fraction of second. The observer at Porthcurno of course made 

 numerous comparisons of his two chronometers by the method of coincidence 

 of beats. 



For further details concerning the methods of observation and reduction 

 employed the reader is referred to the notes and explanations attached, as 

 seemed desirable, to the various tables that follow. 



TABLE I. ERRORS and RATES of the SIDEREAL STANDARD CLOCK of the ROYAL 



OBSERVATORY, GREENWICH. 



M M 2 



